Tani Seiji

The interlayer space of clays is an interesting microenvironment to control the properties of included organic materials. In this study, chromic hybrid films consisting of synthetic saponite (SSA) and fluorescent organic molecules with planar p-conjugated systems were fabricated. The hybrid films exhibited reversible fluorescence color switching induced by swelling and drying, which caused the gallery height of SSA to change. Ultraviolet–visible absorption, steady-state and time-resolved fluorescence measurements of the hybrid films strongly suggested that the organic molecules formed an excimer in the swollen interlayer space of SSA, while they were a monomer in the dried interlayer space. The different emission wavelengths of the excimer and monomer resulted in the fluorescence color switching of the hybrid films. The reversibility of the color switching was maintained for at least 50 cycles with no change of fluorescence maxima. These chromic hybrid films represent a novel approach to obtain color switching.

We have found that X-ray diffraction peaks of clay-organic hybrid films were narrowed after swelling followed by removing of solvent. We fabricated hybrid films consisting of natural montmorillonite (Mont), synthetic saponite (SSA) or synthetic stevensite (SST) and a cationic organic molecule. Full width at half maximum (FWHM) of 001 reflection of as-prepared Mont hybrid was 1.58 2θ degree whereas that after swelling and solvent removing procedure was 0.84 2θ degree. This decreasing of FWHM indicated that the improvement of packing order of clay particles in clay-organic hybrid was occurred during swelling and solvent removing procedure. Similar decreasing of FWHM was also found in hybrids consisting of SSA or SST. Improvement of packing order of hybrid was found to accompany suppression of light scattering of hybrid at the same time.